Thursday, December 26, 2013

Deep Freeze

The temperature at Fairbanks airport touched -40° this morning for the first time this winter.  This is very close to the long-term median date of December 28 for the first -40° reading in Fairbanks, but slightly earlier than the 1981-present median date of January 4.  The long-term median for latest -40° reading is February 10.  Note that -40° is never reached in slightly more than 10 percent of winters in Fairbanks (15 percent since 1981).

It's colder yet at many other interior Alaska stations, including -50 °F in Eagle and -58 °F in Chicken.

The chart below shows the annual number of days reaching -40 °F (total column height) and -50 °F (red columns) in Fairbanks since 1930.  The long-term decline is very noticeable, especially for -50 °F days which have become rare.  However, there was tremendous year-to-year variability prior to about 1975; some winters had few or no extreme cold days, while others had many.  Superficially, it appears that variability has decreased, but this could be an artifact of sampling a smaller portion of the climate distribution in recent decades.


Webcam photos from around Fairbanks show the clear skies and shallow ice fog that are typical in association with deep cold.




20 comments:

  1. Reporting stations above ~5-600' reflect the northerly wind above the inversion bending the exhaust shown in the pics.

    Select all networks to see the temps and wind direction at altitude:

    http://mesowest.utah.edu/cgi-bin/droman/mesomap.cgi?state=AK&rawsflag=3

    This is also seen in the IR shot of warmer grey to the north and west of Fairbanks around the cold white layer of inversion. Look for the warm E>W Tanana Jet in a couple of days as the weather pattern evolves:

    http://pafg.arh.noaa.gov/arhdata/sat/hrpt/13360230804/4f1f.jpg

    Gary @ -40 and ice fog

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  2. Always appreciate dropping by to read your comments on the weather, Rick.

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  3. The increase in average temp in the mid 70's reminded me of the reduction of snow melt as found in the fourth graph as posted on 6 Dec.  This to me suggests, assuming that they are related, that either a station change (as suggested in the snow article) which shows less inversions or there really is a significant multi-decade regime change.  Of course I would be intrigued by the underlying snow physics.

    It would also be cool (pun intended) if we could get multiple soundings throughout the Tanana Valley.  It's -50 in North Pole, -40 near the Airport, -30 Downtown Fairbanks, and -15 in the Hills.  What does the inversion look like at these points?  Has anyone attempted to create a 3D image of an inversion?  So many questions, so few answers... 

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  4. Comments from old timers about weather, some of whom who grew up here from the 1920's onward, often note an increase in wind. Whether it's their recent crop of ear hairs rustling about I don't now, but perhaps it's windier now than they recall from earlier times. Wind can affect the depth and duration of the temperature inversion.

    Historic soundings may reflect those aspects if the balloon's flight direction was observed. I doubt there are many historic remote obs from the hills surrounding Fairbanks until the elevation migration began.

    From the mid-60's onward I don't recall winter wind events in Fairbanks to be as frequent until the '90's.

    Gary

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  5. Gary, you bring up an interesting question: how much does wind affect inversion strength? Are warmer overall temps due to weaker inversions are just plain warmer air masses?

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    1. Not sure of the main driver Eric. Perhaps that's better stated by asking which driver(s) are (or in this case, were) the most seasonally formidable...wind, cloud cover, air mass temp and degree of advection, or solar insolation?

      Surely today it was wind and the temperature of the air overriding the inversion that caused the sudden increase in surface temps. No clouds appeared, and the Sun was briefly 2 deg above the horizon.

      I'm not sure of what historic database exists regarding soundings versus surface temps.

      One thing I've mentioned before is my recollection of the persistence of high clouds during the last PDO warm period (mid '70's - late '90's), but not necessarily the presence of routine wind events in Interior Alaska.

      Gary

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  6. I wonder: has some type of Tanana Jet already begun? Looking at an animation of color-enhanced Suomi NPP VIIRS InfraRed images, you can see what looks like a push of warmer air (cyan to yellow color enhancement) moving from southwest to northeast down the valley: http://go.wisc.edu/92r3y1 Temperatures quickly rise from the -30s to the -Teens F at Delta Junction PABI once the strong ESE winds kick in -- and farther downstream at Nenana PANN temps rise from -32 to -9 F once the ENE winds arrive. I also like how it appears as though a chinook typle of warm surge tries to move southward into the Yukon Flats, but is stopped dead cold by what is likely a formidable inversion. (IR animation with no METAR reports overlaid: http://go.wisc.edu/w90m90)

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    1. I meant moving from southeast to northwest; and sorry about the weird Alaska map projection of the AWIPS images)

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    2. Hey Scott, great animation! I'll bookmark that one for the future. Yup the winds started in the Yukon Flats and blew SW. It was happening for days at some weak level.

      I have a cabin SW of Nenana, South of Manley Hot Springs, and the Wien Lake RAWS to the south of the shack has been reporting wind and relative warmth while Fairbanks/Nenana have been cold.

      Link to RAWS:
      http://mesowest.utah.edu/cgi-bin/droman/meso_base.cgi?stn=WNLA2&unit=0&timetype=LOCAL

      Reader Gary

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  7. Thanks to all for the great comments.

    Scott - that's a fantastic animation showing the impacts of the wind breaking through the inversion. Is anything like this available in realtime on an ongoing basis?

    Eric - I've often thought it would be neat to see a 3D visualization of the inversion, but short of running a very high-resolution numerical model, I'm not sure how it could be achieved.

    Gary - there is wind data in the sounding archive back to 1948, so it would be relatively easy to examine airmass characteristics relative to surface observations. It's on the list.

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    1. The 3D could be done via aircraft/helicopters, or better yet with remote WX drones if there was enough interest. I submit there is below.

      We're experiencing a dramatic increase in poor air quality in the Fairbanks area (http://co.fairbanks.ak.us/airquality/). This is a serious human-weather derived phenomenon that's not going to go away without some serious changes.

      Currently the air quality sampling is surface based, but given the magnitude of the potentially negative effects of PM-2.5 particulates on the local population, I suggest 3-D mapping could explore and define the actual "pollution bowl".

      What better way than airborne sampling to do so? Someone at the U or Gov't should seek a grant. It'd make for a nice tight paper.

      Gary

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    2. Better yet, go LIDAR land mobile and develop a 3-D map.

      Examples:
      http://www.leosphere.com/pdf/BrochureDef_BD.pdf
      http://www.wakenet.eu/fileadmin/user_upload/2nd_workshop/presentations/008-Hannon.pdf
      http://www.sciencedaily.com/releases/2008/08/080826080759.htm

      Gary

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    3. Very nice, Gary. There's some amazing technology available today.

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  8. The Loeospere product looks amazing.

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  9. Local Fairbanks LIDAR: http://www2.gi.alaska.edu/splidar/index.html

    The "News" section is interesting, as is the rest.

    The Principal investigator used to live nearby. My dog barked at theirs.

    Gary

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  10. My physics undergrad research was with mesospheric lidars. We would get the density and thus temperature from 45 - 100 km vertically. I also did a tiny amount of grad research with Dr. Collins. Both lasers took up a room and needed careful calibration. It was fun.

    There are troposphere lidars used to measure temp and winds. But all these lidars are very expensive and not very portable.

    Gary, I like how you sold the idea of sampling particles in the atmosphere. And we don't need anything fancy like military-like drones. Just something that can go up 2000 ft and carry a temp guage and transmitter.

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    1. How about flying a tethered ballon through the inversion with the sampling gear attached? Ok, better let this topic go for now.

      Gary

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    2. I'll chime in one last time. I have a UAS (remote controlled helicopter) and have played around with attaching a hand held personal weather station to it and logging the values. It had mixed success due to weight distribution issues – but that is peculiar to my system. There are laws governing what can be done in the National Airspace and the options are very limited unless you are a government agency. Here are a couple of my videos.

      http://www.youtube.com/watch?v=_AhKTLf_L1I
      http://www.youtube.com/watch?v=EOoHwV57Mcw

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    3. I want one of those copters...what fun! I can see a future in remote tourism and wildlife viewing.

      I'd consider suspending any external load from the CG focus of the UAS via a swivel. Enclosing it in an aerodynamic shell might help reduce interference to the downwash.

      Gary

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  11. Richard: those IR images are screen captures from NWS AWIPS software -- we here at the University of Wisconsin - Madison (and the NWS office in Fairbanks) do receive this VIIRS imagery from the Suomi NPP satellite on a realtime basis, but nothing is posted on the Internet for public access (yet).

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